Diaphragm for acoustical instruments



Hmmm i I"'ru MINIMUM( f Passed Jas.' 7, i930 f D. LA RUE, 0E? EHEMEELEEHEA, PENN SYLVANIA,ASS1GNOR T0 'iTJlClR Tm- ING EMGE'NE MPAUZ, "A ORPGRATION 0F NEW JERSEY d n DHIAGM ACGUSTQAL ENSTRUMENTS aannemen aies eem. sa, trasmessi are.

' This invention relates to diaphragme tor acoustical instruments, and more particularf ly'to diaphragms otn the pleated type.

llt has heretofore been proposed to provide a pleated diaphragm by folding or reversely'iexin a substantially rectangular strip cie suitab e material such, for example, as pa- `bei', the folds extending over the entire suriace of the strip. The opposite ends oi the strip are then suitably secured together; the cylinder thus formed is flexed into a cone, and l i the apex. of said cone is pushed down, the outer ends ofthe pleats openin out and forming the periphery of a dis -like diaphragm. The flattened outer ends of the pleats are then secured in' any desired manner .to a rigid surrounding frame or annular member and the inner ends of said pleats are p secured', as by means of glue, to a center 20 bushin or cylindrical member. 'When so forme ,the ridges resulting from the folding operation extend radially in all directions from said center bushing.

A Ydiaphragm of this character may be formed of large diameter since the same will vibrate as a whole, and as its entire surface is normally under tension it possesses the advantage thhat it will notproduce the disagreeable effect which is technically known as y. blastin or shattering. However, it has been found t at difficulty is sometimes experienced in rendering the diaphragm wholly indifferent to atmospheric changes. Variations in temperature and humidity have a tendency to cause the diaphragm to expand or contract. If the material expands, for example, the pleats tend to pucker, particularly adjacent the rigid supporting ring, and the tension of the diaphragm is reduced. ,Such a condition results in a decrease in the volume and an impairment of the quality of sound produced by the diaphragm. v

An object of the present invention-is to provide a pleated diaphragm which is so 45 formed that it will not be adversely aiected $33,764, and in Great Britain Il, litt.

vby' atmospheric changes, that is, one which is so constructed that atmospheric changes which tend to affect the material of the diaphragm will not result in adecrease in the volume or an impairment ci the quality of sound produced by said diaphragm.

Another ob'ect is to provide a pleated diaphragm whic is so formed that the inner ends of the pleats are arranged tangentially relative to the center bushing, instead of radially. The invention will be readily understood by reference to the accompanying drawings illustrating one embodiment which the inventive idea may assume, and wheremv 1 Fig. 1 is a schematic plan view illustrating 60 the shape of a strip of material that is em- .ployed 1n forming the diaphragm of the present invention;

Fig. 2 is a plan view illustratingthe strip of material shown inl Fig. 1 folded in accordance with the present invention; and

Fig. 3 is a plan view on a larger scale illustrating a diaphragm embodying the present invention.

Referring to the drawings wherein like reference characters refer to like parts throughout the several views, 1 is a strip of any suitable material, for example, paper, of the required width and length as determined by the size of the iinished diaphragm. Taking for example a diaphragm of circular shape, this strip is given the form of a rhomboid, the angle between the ends of the strip and the sides thereof being determined by the amount of oli'set from the radial position which it is desired that the pleats or folds shall have in the finished diaphragm. Thel strip of material is then pleated, or reversely flexed, the pleats running parallel to the ends of the strip throughout the entire surface of the same. When the pleats are formed in the strips, each pleatI is laterally oliset with respect to its adjacent pleats. The opposite ends 2, 3 of the pleated strip are then brought -the fold Where the seam occurs being preferably of the same Width as the remaining folds.

The cylinder now formed is flattened out' into a disk in any suitable Way. This is preferably done by standing the cylinder on one edge, gathering the .opposite ends of the pleats to form a cone, and pushing the apexl of the cone downwardly into the plane of the opposite ends of the pleats, thus forcing the latter to open out. Preferably a cylindrical center bushing 4, which may be formed in any desired manner, is inserted in the apex of the cone before the latter is forced down- Wardly into the plane of the opposite ends of the pleats. The outer periphery of the bushing 4 is preferably covered with a suitable adhesive in order that the inner ends of the pleats may be firmly secured thereto. The usual supporting ring or frame 5 is then attached to the outer ends of the pleats in any suitable or desired manner.

It will be found that the inner ends of the pleats do not abut radially upon the bushing 4 but the lines of the folds lie in planes which are substantially tangent to the outer periphery of said bushing. Said inner ends are secured to the periphery of said bushing and are curved to conform vvith the surface of said bushing, the extent of engagement of said inner ends With said bushing being determined by the angle of the ends of the original rhomboid blank to the long sides thereof.

If a diaphragm thus constructed is subjected to changes in atmospheric conditions whereby the pleats tend to increase or de-I crease in length, the thrust or pull arising from the change in length of the pleats is exerted tangentially on the center bushing 4 so that a slight rotation of said center bushing takes place, the outer ends of the leats While the invention has been being immovably held by the rigid r1ng 5 which acts as an abutment. An increase lin the length of the pleats produces a rotation of the center bushing in one direction, While a decrease in their length produces a rotation in the opposite direction. -By this means any variation in-the length of the pleats is automatically compensated and the diaphragm remains under tension.

It will thus be seen that there is provided a diaphragm which is so constructed as to automatically compensate for changes which tend to vary the volume or to affect the quality of sound produced thereby. Said diaphra In is inexpensive to manufacture and is capa le of producing superior results, and is particularly adapted for use Where it is desired to employ av diaphragm of lar e diameter. cescribed and illustrated as applied to a diaphragm of circular shape, it is to be expressly understood that the invention is not limited to diaphragms of that form, as b suitabl sha in the original blank the reslilting dlaphrlgx may be made of any suitable peripheral conguration. Changes may also be made in the construction of the center bushing and surrounding frame without departing from this invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention. A

What is claimed is:

l. A pleated diaphragm having the pleats thereof disposed tangentially to the center of the same. 2. A diaphragm formed of a stri of material having the outline of a rhom oid, lsaid strip being pleated and flexed into a disk, the pleats running parallel to the short sides of said strip before it is flexed.

3. A diaphragm comprising a strip of pleated material flexed into a disk, and a center bushing, the inner ends of the pleats having tangential engagement with said bushing.

4. A device of the class described comprising, in'combination with a rigid frame member, a pleated diaphragm secured at its outer periphery to said member, and a center bushing secured to the inner edge of said diaphragm, the pleats of said diaphra m extending tangentially from the outer sur ace of said bushing.

5. A device of the class described comprising a ri id frame member, a center cylindrical mem er, and a pleated diaphragm secured to said members, said pleats having'such engagement with the periphery of said center member that expansion and contraction of the diaphragm tends to rotate said center member.

6. A pleated diaphragm having a cylindrical center member with the pleats thereof disposed tangentially to said member.

7 A'pleated diaphragm formed of a rhomboidal strip of material havin folds extending parallel to the short sides o said strip.

8. A diaphragm formed of a strip of material having its ends at an oblique angle to the length of said strip, said strip being folded along lines running parallel to the short sidesI of said strip and flexed into a disk.

. 9. A diaphragm composed of a plurality of elements constituted by pleats, the inner ends of said elements being tangentially arranged relative to the center of the diaphragm, and the outer edge of each element being substantially in a plane normal tothe axis of said diaphragm.

10. A diaphragm having a plurality of elements constituted by pleats, the inner ends of said elements being tan entially arranged relative to the center o the diaphragm, and means to hold said elements in a flexed position, with the outer ends of said flexed elements in a single lane.

11. A device ofpthe class described comprising a center member having a curved outer surface, and. a pleated diphragm, the inner ends of said pleats being attached to saidv member and being curved toconform with the surface of saidA member.

12. A leated diaphragm formed of a strip of material, said strip being folded along lines at an oblique angleto its ed es.

In testimony whereof I ave signed, this specication.

WILLIAM D. LA RUE. 

